Standardization of measurements of 25-Hydroxyvitamin D3 and D2

Abstract

The vitamin D status is increasingly assessed/monitored in different populations, research cohorts and individual patients. This is done by measuring the liver metabolites 25-hydroxyvitamin D3 and D2 as biomarkers. Recommendations for using specific serum concentrations of these biomarkers to assess a person's vitamin D status were done. This requires current vitamin D assays to be sufficiently accurate over time, location and laboratory procedures. In view of the fact that several studies demonstrated that current 25(OH)D measurement methods do not meet this prerequisite, standardization is needed. This paper rehearses the basic concept of standardization, in particular applied to measurements of 25-hydroxyvitamin D. Progress has been made by establishing a reference measurement system consisting of reference methods and reference materials. Coordinated efforts to improve the accuracy and standardize measurements are being performed by organizations such as the U.S. NIH, the CDC and Prevention, the NIST together with their national and international partners. Beyond describing the available reference measurement system and its use as calibration hierarchy to establish traceability of measurements with routine laboratory methods to the SI-unit, this report will also focus on other aspects considered essential for a successful and sustainable standardization, such as analytical issues related to the definition of the measurand and analytical performance goals.

Key Words::

• Analytical performance goals
• 3-epi-25-hydroxyvitamin D
• total 25-hydroxyvitamin D
• traceability
• Vitamin D Standardization Program
• VDSP
• DEQAS

Acknowledgements

The authors acknowledge the interesting discussions on the VDSP with the following colleagues: Paul M. Coates, Director of the NIH/ODS, Chris Sempos, Coordinator of the VDSP on behalf of NIH/ODS, Karen Phinney, Research Chemist and Team Leader mass spectrometric methods, Analytical Chemistry Division, NIST, Rosemary Schleicher, Research Chemist in the Division of Laboratory Sciences, National Center for Environmental Health, CDC, and the Heads of the National Surveys from Australia, Canada, Germany, Ireland, Mexico, South Korea, UK and USA. Last but not least, the authors are indebted to the initiating efforts done by late Mary Frances Picciano, Senior Nutrition Research Scientist, NIH/ODS.

Disclaimer

The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.